diff -r de81e0fe4905 Lib/smtplib.py
--- a/Lib/smtplib.py	Sun Mar 02 20:29:18 2014 +0100
+++ b/Lib/smtplib.py	Mon Mar 03 20:31:21 2014 +0100
@@ -558,12 +558,77 @@
                 if not (200 <= code <= 299):
                     raise SMTPHeloError(code, resp)
 
+    def _pre_authentication(self):
+        self.ehlo_or_helo_if_needed()
+        if not self.has_extn("auth"):
+            raise SMTPException("SMTP AUTH extension not supported by server.")
+
+    def login_auth_plain(self, user, password):
+        """Log in on SMTP server using plain authentication."""
+
+        self._pre_authentication()
+
+        # Encode arguments to SMTP-Syntax.
+        string = "\0%s\0%s" % (user, password)
+        encoded = encode_base64(string.encode('ascii'), eol='')
+
+        (code, resp) = self.docmd("AUTH", "PLAIN %s" % encoded)
+        # 235 == 'Authentication successful'
+        # 503 == 'Error: already authenticated'
+        if code in (235, 503):
+            return (code, resp)
+        raise SMTPAuthenticationError(code, resp)
+
+    def login_auth_cram_md5(self, user, password):
+        """Log in on SMTP server using CRAM-MD5 authentication."""
+
+        self._pre_authentication()
+
+        # Get challenge from Server and encode arguments.
+        (code, challenge) = self.docmd("AUTH", "CRAM-MD5")
+        challenge = base64.decodebytes(challenge)
+        response = user + " " + hmac.HMAC(password.encode('ascii'),
+                                          challenge, 'md5').hexdigest()
+        encoded = encode_base64(response.encode('ascii'), eol='')
+        if code == 334:
+            (code, resp) = self.docmd(encoded)
+
+        # 235 == 'Authentication successful'
+        # 503 == 'Error: already authenticated'
+        if code in (235, 503):
+            return (code, resp)
+        raise SMTPAuthenticationError(code, resp)
+
+    def login_auth_login(self, user, password):
+        """Log in on SMTP server using LOGIN authentication."""
+
+        self._pre_authentication()
+
+        # Send username and password to server.
+        (code, resp) = self.docmd("AUTH",
+            "%s %s" % ('LOGIN', encode_base64(user.encode('ascii'),
+                                                 eol='')))
+        if code == 334:
+            (code, resp) = self.docmd(encode_base64(password.encode('ascii'),
+                                                    eol=''))
+
+        # 235 == 'Authentication successful'
+        # 503 == 'Error: already authenticated'
+        if code in (235, 503):
+            return (code, resp)
+        raise SMTPAuthenticationError(code, resp)
+
     def login(self, user, password):
         """Log in on an SMTP server that requires authentication.
 
         The arguments are:
-            - user:     The user name to authenticate with.
-            - password: The password for the authentication.
+            - user:           The user name to authenticate with.
+            - password:       The password for the authentication.
+
+        Optional parameter:
+            - auth_encoder:   Function used to generate the string to send to
+                              server based on username and password. Must take
+                              exactly this two arguments and return a string.
 
         If there has been no previous EHLO or HELO command this session, this
         method tries ESMTP EHLO first.
@@ -580,24 +645,11 @@
                                   found.
         """
 
-        def encode_cram_md5(challenge, user, password):
-            challenge = base64.decodebytes(challenge)
-            response = user + " " + hmac.HMAC(password.encode('ascii'),
-                                              challenge, 'md5').hexdigest()
-            return encode_base64(response.encode('ascii'), eol='')
-
-        def encode_plain(user, password):
-            s = "\0%s\0%s" % (user, password)
-            return encode_base64(s.encode('ascii'), eol='')
-
         AUTH_PLAIN = "PLAIN"
         AUTH_CRAM_MD5 = "CRAM-MD5"
         AUTH_LOGIN = "LOGIN"
 
-        self.ehlo_or_helo_if_needed()
-
-        if not self.has_extn("auth"):
-            raise SMTPException("SMTP AUTH extension not supported by server.")
+        self._pre_authentication()
 
         # Authentication methods the server claims to support
         advertised_authlist = self.esmtp_features["auth"].split()
@@ -617,26 +669,22 @@
         # support, so if authentication fails, we continue until we've tried
         # all methods.
         for authmethod in authlist:
-            if authmethod == AUTH_CRAM_MD5:
-                (code, resp) = self.docmd("AUTH", AUTH_CRAM_MD5)
-                if code == 334:
-                    (code, resp) = self.docmd(encode_cram_md5(resp, user, password))
-            elif authmethod == AUTH_PLAIN:
-                (code, resp) = self.docmd("AUTH",
-                    AUTH_PLAIN + " " + encode_plain(user, password))
-            elif authmethod == AUTH_LOGIN:
-                (code, resp) = self.docmd("AUTH",
-                    "%s %s" % (AUTH_LOGIN, encode_base64(user.encode('ascii'), eol='')))
-                if code == 334:
-                    (code, resp) = self.docmd(encode_base64(password.encode('ascii'), eol=''))
-
-            # 235 == 'Authentication successful'
-            # 503 == 'Error: already authenticated'
-            if code in (235, 503):
-                return (code, resp)
+            try:
+                if authmethod == AUTH_CRAM_MD5:
+                    (code, resp) = self.login_auth_cram_md5(user, password)
+                elif authmethod == AUTH_PLAIN:
+                    (code, resp) = self.login_auth_plain(user, password)
+                elif authmethod == AUTH_LOGIN:
+                    (code, resp) = self.login_auth_login(user, password)
+                # 235 == 'Authentication successful'
+                # 503 == 'Error: already authenticated'
+                if code in (235, 503):
+                    return (code, resp)
+            except SMTPAuthenticationError as e:
+                last_exception = e
 
         # We could not login sucessfully. Return result of last attempt.
-        raise SMTPAuthenticationError(code, resp)
+        raise last_exception
 
     def starttls(self, keyfile=None, certfile=None, context=None):
         """Puts the connection to the SMTP server into TLS mode.